Design and Implementation of a SEPIC Topology DC-DC Converter

Simplicity in any circuit design is important including DC-DC converter designs. Textbooks used to teach students about DC-DC converters are seldom the entire circuit from start to finish, instead relying on abstract concepts to simplify the circuit as much as possible. This paper introduces a buck DC-DC converter design -using a SEPIC topology- and prototype based on using the well-known 555 timer to generate a PWM signal and an op-amp used as a simple two pole voltage controller. This study will examine similar non isolated DC-DC converter topologies capable of buck conversion and how their implementation becomes more difficult and complex as the location of the switching MOSFET is moved from low-to-high side control. The results of the analysis revealed SEPIC based converters are the easiest non isolated DC-DC converter topology with a non inverting output to use as a buck converter implemented using common components such as 555 timers, op amps, inductors, capacitors, resistors, diodes, a reference IC, and a mosfet while also achieving an acceptable quiescent current and efficiency.